A guide wire is used to facilitate insertion of a catheter into a lumen (such as digestive tract and blood vessel) of a living body. It leads a catheter slipped thereon to a desired position in a lumen.
A guide wire is also used to lead a catheter to a desired position in a lumen of a living body through an endoscope or a lumen of an endoscope at the time of observation or treatment of a lumen of a living body.
A guide wire for this purpose has a marker on its surface which tells its position and movement during insertion. A guide wire in a single color without a marker cannot be recognized for its movement when it turns around its axis. There have been proposed several methods for attaching a marker to a guide wire.
One method is described in U.S. Pat. No. 5,379,779 and involves slipping a hollow tube of polytetrafluoroethylene (PTFE), having one or more colored spiral pattern, onto a core wire and subsequently allowing it to be heat-shrink around the core wire of a guide wire.
Another method described in U.S. Pat. No. 6,811,958 involves adding a color producing agent (such as mica which produces a color upon irradiation with a laser beam) to the covering layer on the core of the guide wire and irradiating the covering layer with a laser beam for color development, thereby forming a marker as desired.
The above-mentioned guide wires include those which have surface irregularities formed thereon.
An example is disclosed in U.S. Patent Application Publication No. 2006/116609 in which the guide wire has a curved part on which surface irregularities are formed so as to make it more flexible. This guide wire has its surface irregularities formed from the outermost layer which is partly removed by heating a coil wound around the curved part at prescribed intervals.
In addition, observation or treatment of an intracorporeal lumen or the like by use of an endoscope is also known, and a guide wire is again used by which the endoscope or a catheter inserted in the lumen of the endoscope is guided to the target site of the intracorporeal lumen or the like.
During insertion of the guide wire, the guide wire is moved along the axial direction thereof while it is rotated about its axis. These operations are carried out while visually checking the guide wire under fluoroscopy or through an endoscope. If the guide wire is monochromatic, it cannot be seen whether or not the guide wire is moved as intended. Some guide wires are provided at their surfaces with markers (marks) for indicating the position or the like. An example is disclosed in Japanese Patent Laid-open No. 2001-46508. Here, the guide wire mark is helical.
During use of the guide wire described in the aforementioned document, whether the guide wire is moved along its axial direction or rotated about its axis, each portion of the helical mark which is visually checked in practice (each belt-like portion cross-hatched in FIG. 3(b) of the document) appears to be moving to change in one direction, for example, in the distal direction. Therefore, even when the guide wire is rotated about its axis by applying torque, the operator might perceive that the guide wire is moving distally or proximally, contrary to what was intended, and this may cause a mis-steering of the guide wire.